Navigate to another screen

[shqipesejdiu]

when I dont have connection i cant navigate to another screen.
error: I/flutter (11947): Another exception was thrown: 'package:flutter/src/widgets/navigator.dart': Failed assertion: line 1420 pos 12: '!_debugLocked': is not true.
to navigate to another screen i use this:
Navigator.push(
context,
MaterialPageRoute(
builder: (context) => new ThankYouPageState(),
),
);